This invention relates generally to techniques for reproducibly transferring patterns to semiconductor devices and particularly to techniques which do not require the use of expensive steppers or the like. The techniques have applicability, for example, in connection with the formation of field emission displays.
In the manufacture of most modern semiconductor devices, a pattern is repeatedly transferred to a substrate using a device called a photolithographic stepper. The stepper is a highly precise machine which may use ultraviolet light to transfer an image formed on a glass plate called a reticle or mask to the semiconductor substrate. For example, the image may be transferred by shining light through the stepper reticle which has an enlarged version of the desired pattern formed on it. The light pattern created by the reticle pattern causes the photoresist to be exposed in the desired pattern. Photoresist can then be developed and etched depending on whether or not it was exposed to light. The photoresist develops differently based on light exposure, and therefore the pattern formed on the reticle in the stepper can be accurately transferred to the substrate.
In many instances, it may be necessary to transfer a pattern reproducibly to a substrate, but the degree of precision enabled by modern stepper technology may not be absolutely required. Because the stepper equipment is extremely expensive, it would be desirable to develop a process which allows patterns to be transferred without requiring the use of expensive stepper technology.
One approach to avoid a resist mask step is found in U.S. Pat. No. 4,407,695 entitled "Natural Lithographic Fabrication of Microstructures Over Large Areas" to Deckman et al. ("Deckman et al. '695"). Deckman et al. '695 describes forming a mask by depositing an ordered, closely packed monolayer of colloidal particles on a substrate. The particles may be arranged in the monolayer as an array. The array serves as a lithographic mask for etching the substrate.
Another approach to avoid a resist mask step for forming field emitter tips is found in U.S. Pat. No. 5,399,238 entitled "Method of Making Field Emission Tips Using Physical Vapor Deposition of Random Nuclei as Etch Mask" to Kumar ("Kumar '238"). Kumar '238 describes physical vapor deposition of randomly located, discrete nuclei. The nuclei are deposited on an emitter tip material, and form a discontinuous etch mask thereon. Using an ion etch, the emitter tips are formed with aid of the nuclei etch mask.
It would be desirable to have an economical technique for transferring patterns to semiconductor substrates that does not necessitate the large capital investment inherent in stepper technology.